Purchased in 2016..! Used very frequently mainly for charging 18650 batteries but also all AAA batteries for TV remotes, air conditioners, and other household electrical devices. Still works 8 years after purchase. It has exceeded all expectations!

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It finally broke down after about 9 years!
It started making an annoying noise (like a whistle or static from old televisions) every few seconds.
After a few weeks, it started blinking during charging.
So I bought another Nitecore again, the UM2.
I no longer need 4 slots, 2 are enough.

Good charger, beautiful and correct in its use, but unfortunately after its warranty expired, it left me. It was reading that it was charging without having batteries on it and it was not charging the batteries when I placed them and it was giving an error... it went to the trash...

I had some new Nitecore batteries for a flashlight that I had forgotten for a long time and they were not charging, but with this charger they charged. So, everything is fine.

I know the company from its lenses, which are top-notch in many areas.
I have had the charger for a few days and have tried various batteries. It charges them quickly, although some get excessively hot. It recognizes them correctly and overall I haven't seen any other problems so far.
The screen is clear, with indications for battery type, percentage, duration, and charging amperage, as well as battery voltage.
I hope it proves to be as high-quality and durable as their lenses.
4 stars for the quality of the buttons, which feel ready to fall off and have nothing to do with the quality of the nitecore. Maybe I'm being unfair to them, but for 40 euros I think they needed a little more attention there.

The most reliable and secure battery charger.
Especially for the nitecore batteries I use. It's not the cheapest, but it's definitely the best.

I bought it too for the Cretans, it doesn't recognize problematic batteries, resulting in one exploding. I don't know if it was the battery's fault. The charger overheated, so if you use it, make sure to keep a safe distance. Otherwise, it charges the batteries quickly. And a request, please also mention which chargers you have purchased so that mistakes can be avoided. I would like to point out that the battery simply exploded, there was no issue with fire or anything related. I don't know if this is a positive thing, it just exploded and flew away. After 2 years of minimal use, it overheats and struggles. I wouldn't say it's a good choice until the batteries are fully charged... while in another Chinese product with longer charging time, the same batteries didn't burn so much.

I saw various reviews to come to a conclusion, and I think it was worth it. I am putting my batteries to charge and I am not afraid that my house will catch fire.

Very good charger! It fully charges our batteries reliably and in a reasonable amount of time. 4 18650 batteries of 3000mAh require 7-8 hours. I highly recommend it without reservation!!!

I bought the NiteCore D4 charger because of the reviews, I admit that I didn't know this particular brand and I was impressed by the positive comments. In practice, if you slightly touch the batteries during charging, the charger goes crazy and even though the battery is supposed to be fully charged, it shows empty. Similarly, batteries that still needed time to charge are shown as full. How is it possible for a battery that has been fully charged to need an extra 2 or 3 hours to charge again? Doesn't it understand that it's already full? I have never encountered such a thing with any other charger, I find it unacceptable... The tests were done with eneloop batteries from the package. The Technoline BC 700 that I had was superior

This charger works for what it has been designed without posing any known risks and issues compared to others.

Aristos and with the volts you see and everything. I also put 21700 batteries and they fit perfectly!

4 years later and it still charges! It doesn't understand anything. If it could also measure the battery's mah, it would be the best. I would like to say that an old 18650 battery I had dropped to 0.9 volts and slowly brought it back, it works wonders.

In such products, you choose a branded one and not a cheap Chinese one that is more likely to set your house on fire. The name NiteCore says it all, no need for special recommendations.
POSITIVES:
- Recognizes the type of battery you insert
- Clear display showing charging time, volts, and milliampere-hours of charge
- Stops charging separately for each element to prevent overcharging
- You can select milliampere-hours of charge separately for each element
- Ability to turn off the display while on standby or during charging
- Accepts multiple types of batteries
NEGATIVES:
- Does not have a standard option for milliampere-hours, for example (if you insert 4 batteries for charging, the low option gives 150mla, while if you insert 2, the low option is 300mla). This is why I give it 4 stars, otherwise I am satisfied

Very good, I had bought various chargers from China but they were not reliable.
With NiteCore, I can see what's happening on the screen and I don't worry about it catching fire when I'm away.

I have had this particular product in my possession for a month now and I can confidently say that it is excellent in terms of its performance and build quality. Personally, I haven't tried many chargers of this scale, but I know from information that they tend to heat up quite a bit, and the same goes for this one. It could have a better thermal dissipation system. On the screen, they have incorporated several indicators (time, speed, volt, start, end of charging), but nothing related to the battery health, and I consider this to be a significant omission for such a charger. So, 4 stars

Fast and reliable (at least so far).
I operate it with rechargeable 18650 and AAA batteries.

It shows quite a quality charger and the screen is readable with all the basic indicators. The charging time is not among the best on the market, a 3000mAh 18650 battery takes 4+ hours and the more batteries are in the charger, the longer the time increases. After a few months of use, a slight whistling sound can be heard when it is connected to power, which I don't know if I should be concerned about. However, compared to what is available, it is one of the good purchases.

All my batteries are rechargeable eneloop from Panasonic and recently I have the 18650 3500mah from Nitcore due to flashlights. I no longer deal with alkaline and regular batteries because they are more expensive, while with rechargeable ones you can recharge them as much as you want. Consider that eneloop batteries have a charging-discharging cycle of 1500 times and their performance only drops by 70%. The charger is very reliable with a capacity mah and voltage Volt information screen. Also, when the battery charging is complete, it stops and notifies you, it does not continue to charge continuously so there is no risk of explosion! Generally, it heats up during charging but it is normal. It charges almost all types of batteries.

Very good charger with full battery charging status update for each one separately. AAA batteries will give you a little trouble to bring them into contact with the terminals. It took about 8 hours to charge 4 18650 batteries to full charge at 4.1 volts instead of 4.2.
The time seems sufficient for lithium batteries, and also the total charge is 99% and not 100%

I have bought several chargers but I have never seen one like this before! It has a beautiful screen displaying battery information and it charges batteries that other chargers cannot. Get it if you want a good tool, but make sure to also get branded batteries...

I purchased the charger 6 months ago due to frequent battery changes in power-hungry devices such as game controllers, etc. I have tested it with AAA and AA batteries, as well as 18650 batteries. In addition to regular charging, it also provides the ability to charge at lower and longer durations for batteries that require it, such as Ikea rechargeable batteries. Additionally, each slot operates independently, meaning you can charge different batteries with different charging methods in each one. During charging, it displays various information such as battery voltage or charge level. The screen backlight can be turned off to avoid disturbance at night. So far, I am very satisfied.